The investigator proposes to study requirement for 5' and 3' processing of tRNA in cells of Drosophila melanogaster. Both RNase P, required for 5' end processing, and 3'-tRNase will be isolated and characterized as to their macromolecular composition. Since RNase P generally has an RNA component, any RNA copurifying with Drosophila RNase P will be sequenced in order to make phylogenetic comparisons with RNAs associated with RNase P in other species. Site specific mutations will be introduced into tRNA to analyze requirements for substrate recognition and catalysis. Three questions will be addressed in these studies: 1.) How do the elements of tRNA structure recognized by RNase P and 3'-tRNase differ from each other? 2.) Does either enzyme recognize a specific sequence, or only structure? and 3.) To what extent do tertiary contacts (e.g., between the D and T loops) contribute to substrate recognition?